- Background: Small bowel obstruction after Roux-en-Y gastric bypass (RYGB) can be difficult to diagnose, but usually requires surgical treatment; clinical presentation may be nonspecific. Delay in diagnosis can result in catastrophic outcomes. Patients who present with small bowel obstruction after gastric bypass occasionally have pancreatic enzyme elevation and have been misdiagnosed as having acute pancreatitis. The objective of this study was to determine if there was an association between small bowel obstruction and an elevated amylase or lipase after RYGB. Methods: Ninety-nine cases of small bowel obstruction treated surgically were prospectively collected and retrospectively analyzed from a database of 4014 RYGB patients. Fifty-eight had a measurement of amylase or lipase at the time of operation. Results: An elevated amylase or lipase was found in 48% of all patients. These elevated rates were higher in an acute obstruction compared to those presenting with chronic symptoms (64% versus 28%; P=.007) and in obstruction involving the biliopancreatic limb compared to those that did not involve that limb (65% versus 21%; P<.001). These elevated rates were most notable in acute biliopancreatic limb obstruction compared to an acute obstruction not in the biliopancreatic limb (94% versus 27%; P<.001). Conclusion: In RYGB patients, there is an association between small bowel obstruction and an elevated amylase or lipase. Acute obstruction of the biliopancreatic limb can be difficult to diagnose, and in these patients, the sensitivity of elevated amylase or lipase is very high. RYGB patients with abdominal pain should have their amylase and lipase measured. It is important to recognize that an elevation of these enzymes is not likely a result of acute pancreatitis.